The present disclosure relates, in general, to knee bolsters used in vehicles to protect the knees of vehicle occupants, such as during the event of a collision or crash. More particularly, the disclosure relates to an improved knee bolster that is easier to manufacture, assemble in a vehicle and/or provides an improved stepped crush (i.e., controlled deflection) when forcibly impacted. In one embodiment, the improved knee bolster employs varied shapes, thicknesses and/or dimensions to create multiple (e.g., two) crush zones for providing a multiple-step deflection versus force curve, i.e., a particular stepped crush, wherein the crush zones collapse sequentially when a sufficient force is applied to the knee bolster, such as a knee impacting the knee bolster during a collision. The improved knee bolster will be described with particular reference to this and like embodiments, but it is to be appreciated that it is also amenable to other like applications.
In general, it is well known to use a knee bolster on or adjacent a vehicle's front dashboard, such as on either side of the vehicle's steering column extending from the front dashboard. Examples of such an arrangement are provided in U.S. Pat. No. 5,037,130 to Okuyama and U.S. Pat. No. 5,370,417 to Kelman et al., both expressly incorporated herein by reference. Another knee bolster example is disclosed in commonly-owned U.S. Pat. No. 4,893,834, also expressly incorporated herein by reference.
It is also known to attempt to control the crush (i.e., deflection relative to impact force) of a knee bolster. Various types of knee bolsters have been proposed for this purpose. Examples of such knee bolsters are disclosed in U.S. Pat. No. 5,273,314 to Sakakibara; U.S. Pat. No. 5,549,327 to Rüsche et al.; and U.S. Pat. No. 6,609,727 to Figlioli et al., all expressly incorporated herein by reference. The '314 and '727 patents disclose step-shaped knee bolsters, whereas the '327 patent discloses a knee bolster having a wall with a progressively dimensioned thickness for purposes of controlling the rate of crush.
However, these and other prior art knee bolsters are not always suitable for and/or do not necessarily fit properly within particular vehicle layouts. Further, many conventional knee bolsters are bolt-on structures and not typically formed of a material that lends itself to being welded to a vehicle frame or body, such as when the frame or body is formed of aluminum. In view of the foregoing, there is a need for a knee bolster which can be fit into specific vehicle layout configurations. Moreover, there is a need for a knee bolster that can be formed of a preferred material, such as aluminum for example, that allows for a welded connection to an underlying vehicle structure, such as an aluminum vehicle frame.
There also always remains a need for knee bolster exhibiting improved crush or deformation characteristics. In particular, an optimally designed knee bolster will allow a specified force to pass through the knee bolster to a vehicle occupant's femur bone during a collision, the specified force being a threshold force that is considered the highest reasonable force able to be absorbed by a vehicle occupant's femur bone without breaking or fracturing the same. Allowing the femur bone of a vehicle occupant to absorb the highest reasonable force possible without breaking or fracturing has the effect of reducing as much as possible the amount of force imparted on the occupant's chest or other body portions during a collision. In the case where the vehicle occupant is the driver, allowing the driver's femur bone to receive the maximum possible reasonable force without breaking or fracturing directly reduces the amount of force imparted to the driver's chest from the steering column during a collision.
Other considerations supporting the need for an improved knee bolster include the overly complex construction of prior art knee bolsters which often requires complicated and/or costly processes for making the components that ultimately form the knee bolster. In addition, prior art knee bolsters often require difficult assembly procedures for assembly and/or installation into a vehicle. Still further, prior art knee bolsters are often difficult to modify for purposes of adjusting responsiveness to impact loads applied thereagainst.